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Re: starship-design: Re: Perihelion Maneuver

L. Parker wrote:
>On Monday, December 01, 1997 7:35 AM, Isaac Kuo [SMTP:kuo@bit.csc.lsu.edu] 

>> Huh?  What?  You're saying that car speeds are governed by highway
>> speed limits on race tracks?

>IMSA and NASCAR have required governors on race vehicles for years...

But not to highway speed limits.

>> The size of the engines are smaller, but not much lighter.

>Hmm, you should try to lift the four cylinder engine in my old Willy's 

I don't feel like lifting a 4 cylinder engine in a 1997 model
full size sedan either.

>> >Theres no reason to since the military personel of today can't point
>> >significantly more acurately then those of 40-50 years ago.

>> Actually, there is every reason to increase the performance of small
>> arms in terms of reducing ammo size/weight, which has a dramatic
>> impact on logistics.  (It also allows carrying more ammunition and
>> weight).  Also, if ammunition size/weight can be dramatically reduced,
>> it allows firing much larger bursts, which _does_ increase hit
>> probability.

>Actually, when the US Army went looking for a new weapon to replace their 
>WWII vintage rifles their was quite a bit of heated debate.

Yes they did.  There has been a _lot_ of effort put into finding
something a lot better to equip our infantry with.  However,
we never have dramatically improved the small arm since the
development of the assault rifle.

>It seems that 
>of all the ammunition expended in WWII only one round in a million actually 
>hit someone. One faction wanted to purchase a more accurate semi-automatic 
>weapon and force the troops to learn to AIM them.

>The other faction claimed that the lives of our soldiers were more 
>important than hitting a target and that this would be best achieved with a 
>fully automatic weapon that would at least (hopefully) force the enemy to 
>keep their heads down whether we hit anything or not. As you can see, the 
>M14 lost and the M16 won. Guess which weapon is preferred by special forces 
>snipers and civilian competition shooters?

The M14 and M16 are not that different, really.  Neither is twice as
much anything compared to the other.

OTOH, imagine what effect reducing ammunition size/weight to 1% of
a 5.56mm round could have.  With 2000 round magazines, every
infantryman would have the firepower of a squad level support weapon,
and could afford to fire 15 round bursts all day.  Even with the
increased expenditure of ammo, logistics would be greatly simplified,
with enough ammunition for a platoon being able to be carried by a
single person.

But you'll just have to imagine it, because it's not going to happen
in the foreseeable future.

>> However, the physics of aerodynamics and chemistry of explosives has
>> prevented us from making any dramatic advances in small arms.
>> Logistics concerns _have_ prompted reducing ammo size/weight, but
>> at the expense of performance.

>There have in fact been a plethora of advancements in both weapon and 
>ammunition size, weight, and performance.

Small advancements, yes.  Significant ones, yes.  But dramatic
advances?  A WWII era BAR still looks pretty good after all
these years.

>These in turn have necessitated 
>improvements in armor and tactics as well. Even so, modern body armor is no 
>match for the weapons that are now freely available on the market - weapons 
>that have been developed in the last few years. Just ask your local 

Umm...modern body armor is no match for the weapons feely available
in the 19th century.  A vintage Winchester .30'6 will slice through
a "bulletproof vest" just as readily as a modern .30 hunting rifle.

Modern police body armor is meant to deal with low power pistols
and maybe certain shotgun loads, but never had a chance against
a rifle.

Military body armor is meant to deal with shrapnel (on a lucky day).

>Scientific and technological advancements tend to run in cycles, short 
>spurts followed by a period of consolidation and incremental improvement. 
>Most theorist think that we are nearing the end of a slow period and should 
>begin seeing new breakthroughs in the next twenty years. If for no other 
>reason than the sheer amount of new information that we are acquiring.

Getting back to the point of this discussion, I was making the claim
that 10%c was good enough to start launching flyby probes.

Kelly disputed this, and among other things noted that you wouldn't
launch such a thing if you only had to wait a couple decades to
acheive better.

I replied saying that you would if you didn't think those next
couple decades would make enough of a difference.

To put some perspective on this, consider a flyby mission to
Alpha Centauri which are around 4 light years away.  A 10%c
mission would get there in 40 years from the launch date.
What if we wait 20 years?  _If_ those 20 years allow launching
a 20%c probe, then it could get there as fast as the earlier
mission possibility.

Can you bet on doubling performance in just 20 years?  Maybe,
maybe not.  There are plenty of examples of technology which
haven't "doubled" their performance in as much time.
    _____     Isaac Kuo kuo@bit.csc.lsu.edu http://www.csc.lsu.edu/~kuo
/___________\ "Mari-san...  Yokatta...
\=\)-----(/=/  ...Yokatta go-buji de..." - Karigari Hiroshi